Commit 9db4e438 authored Mar 27, 2011 by Mikhail Kshevetskiy Committed by Greg Kroah-Hartman Apr 19, 2011

tty/n_gsm: fix bug in CRC calculation for gsm1 mode



Problem description:
  gsm_queue() calculate a CRC for arrived frames. As a last step of
  CRC calculation it call

    gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->received_fcs);

  This work perfectly for the case of GSM0 mode as gsm->received_fcs
  contain the last piece of data required to generate final CRC.

  gsm->received_fcs is not used for GSM1 mode. Thus we put an
  additional byte to CRC calculation. As result we get a wrong CRC
  and reject incoming frame.

Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy@gmail.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

parent 5680e941

drivers/tty/n_gsm.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -1658,8 +1658,12 @@ static void gsm_queue(struct gsm_mux *gsm)

		if ((gsm->control & ~PF) == UI)
		gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf, gsm->len);
		/* generate final CRC with received FCS */
		if (gsm->encoding == 0){
		/* WARNING: gsm->received_fcs is used for gsm->encoding = 0 only.
		In this case it contain the last piece of data
		required to generate final CRC */
		gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->received_fcs);
		}
		if (gsm->fcs != GOOD_FCS) {
		gsm->bad_fcs++;
		if (debug & 4)

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